Trond Myklebust 51fd2eb52c NFSv4: Fix races in the legacy idmapper upcall ...

nfs_idmap_instantiate() will cause the process that is waiting in
request_key_with_auxdata() to wake up and exit. If there is a second
process waiting for the idmap->idmap_mutex, then it may wake up and
start a new call to request_key_with_auxdata(). If the call to
idmap_pipe_downcall() from the first process has not yet finished
calling nfs_idmap_complete_pipe_upcall_locked(), then we may end up
triggering the WARN_ON_ONCE() in nfs_idmap_prepare_pipe_upcall().

The fix is to ensure that we clear idmap->idmap_upcall_data before
calling nfs_idmap_instantiate().

Fixes: e9ab41b620 ("NFSv4: Clean up the legacy idmapper upcall")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

2022-07-13 17:46:52 -04:00

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